1. Field of the Invention
The present invention relates to a hammer device in which a hammer is moved to strike a recording sheet by attraction of an armature with a coil.
2. Description of the Prior Art
In the field of electronic typewriters and computer terminal printers, there are already employed impact printers in which a magnetic force obtained by energizing a coil is used for displacing a movable hammer toward a platen, thereby causing a type to strike a printing sheet on the platen through an ink ribbon to print on the sheet.
In such impact printers, the printed characters will not be uniform unless types of smaller areas exert a weaker striking force while types of larger areas exert stronger striking force.
In order to prevent such drawback there have been made various proposals, but such proposals invariably involve excessive complication in structure or in control.
Also there is required an exact positional adjustment among the hammer, coil and yoke in order to obtain the above-mentioned characteristic of the hammer, but such adjustment is generally extremely difficult and is scarcely achievable in uniform manner on all units.